[R] Largest N Values Efficiently?

[Frede Aakmann Tøgersen]

On my system

>system.time(x1 <- sort(x,decreasing=TRUE)[1:1000])
   user  system elapsed 
   0.03    0.00    0.03 

whereas

> system.time(x1 <- x[order(x)][1:1000])
   user  system elapsed 
   0.11    0.00    0.11 


I.e. using sort is about 30 times faster.


Best regards

Frede Aakmann Tøgersen
Scientist


UNIVERSITY OF AARHUS
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> -----Oprindelig meddelelse-----
> Fra: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] På vegne af David Katz
> Sendt: 12. november 2007 00:44
> Til: r-help at r-project.org
> Emne: [R] Largest N Values Efficiently?
> 
> 
> What is the most efficient alternative to x[order(x)][1:n] 
> where length(x)>>n?
> I also need the positions of the mins/maxs perhaps by 
> preserving names.
> 
>  Thanks for any suggestions.
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